The restoration of soft tissue defects from trauma, surgical excision or congenital defects should start with a strategy that will maintain tissue size and shape to near normal dimensions for extended time frames. Current clinical strategies include free fat transfers and artificial fillers. In the case of breast cancer patients receiving mastectomies, silicone shells filled with saline or silicone are used to replace the void. This leaves the patient with an unnatural look and feel, and the risk of capsular contracture resulting in a revision surgery. The fat grafting and artificial filler options fail to retain volume over time. Thus, the fat grafting and artificial filler options can require a second surgical site, have avascular necrosis and generally do not regenerate the original tissue.
Bovine and human collagen have gained widespread use as injectable materials for soft tissue augmentation and filling. Collagen, the principal extracellular structural protein of the animal body, has been used as an implant material to replace or augment connective tissue, such as skin, tendon, cartilage and bone. Additionally, collagen has been injected or implanted into the human body for cosmetic purposes for a number of years. However, the use of collagen in soft tissue augmentation and/or filling could be costly and it does not have a long lasting effect, e.g., the results often only last for about 3 months.
Hyaluronic acid (HA) is a glycosaminoglycan that is naturally found in the human body and is widely distributed throughout connective, epithelial, and neural tissues. Compositions of non-crosslinked hyaluronic acid tend to degrade within a few months after injection and thus require fairly frequent reinjection to maintain their soft tissue augmenting effect. More recently, compositions of cross-linked hyaluronic acid have been used for soft tissue augmentation. However, such cross-linked compositions contain fairly large particles, around approximately 2 mm each, of hyaluronic acid suspended in a gel. While the larger particles could have a longer lasting effect, the larger particle size can make the injection more challenging and create an unpleasant experience to a recipient.
In summary, the major disadvantages of the current strategies for soft tissue regeneration, repair and/or augmentation include a large amount of tissues required for grafting large tissue defects; donor site morbidity, possibility of second surgical site, avascular necrosis; loss of shape and/or size of the scaffolds over time; material mismatch with native tissue; and failure to regenerate tissue. Accordingly, there is a strong need to develop a strategy or a scaffold that can be administered with a minimally invasive procedure and will provide sustained retention of volume restoration for at least 3 months or longer, e.g., for at least 6 months or at least one year, while the body gradually remodels and regenerates the site into near-normal tissue structure and function.